1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to elevator systems in which the speed of an elevator car is controlled by a speed pattern generator.
2. Description of the Prior Art
U.S. Pat. No. 3,774,729, which is assigned to the same assignee as the present application, discloses an elevator system in which a speed pattern generator controls the speed of an elevator car by providing a time based speed pattern which accelerates the elevator car to, and then maintains, a predetermined running speed. When the elevator reaches a predetermined position relative to a target floor, the speed pattern generator substitutes a distance based speed pattern for the time based pattern, to control the speed of the elevator car during the slow-down phase of the run.
In order to provide a high quality ride, without noticeable "bumps" in the elevator car during a run, the transfer from the time based or running speed pattern to the distance based slowdown speed pattern must be stepless, i.e., the patterns must match at transfer time. Further, in order to provide a comfortable ride, the slowdown must be made at a constant deceleration rate.
In the hereinbefore mentioned U.S. Patent, pattern transfer from the running speed pattern TRAN to the slowdown speed pattern DSAN is initiated after the running speed pattern has entered a slowdown phase, with transfer occurring when the running speed pattern reaches a preset maximum deceleration rate. Excellent performance is achieved when the pattern magnitudes match at the time of transfer, and the deceleration rate of the slowdown speed pattern is the same as the predetermined maximum deceleration value which was used to initiate pattern transfer.
In my co-pending application Ser. No. 073,822 filed Sept. 10, 1979 now U.S. Pat. No. 4,261,439, entitled "Elevator System" I disclosed an improvement for the elevator system of U.S. Pat. No. 3,774,729 in which the slowdown speed pattern DSAN is forced to match the running speed pattern TRAN prior to transfer between the speed patterns. Prior to pattern transfer, the invention of the co-pending application also automatically and continuously determines the deceleration rate to be used by the slowdown speed pattern after transfer, such that by freezing the deceleration rate at the value determined at the precise time of transfer, the elevator car will be decelerated at a constant rate, and the slowdown speed pattern will have a predetermined value when the elevator car is at a predetermined location relative to the target floor, enabling stepless transfer at this predetermined location from the slowdown speed pattern DSAN to a landing speed pattern HTAN which is initialized to the predetermined value.
The present invention is an improvement on my co-pending application, improving ride quality and eliminating bumps in the car during pattern transfer from the running speed pattern to the slowdown speed pattern, regardless of the deceleration rate which will be used by the slowdown speed pattern after pattern transfer.